The purpose of this project is to discover additional biochemical gene markers in the mouse that will enhance our understanding of the organization and evolution of the mammalian genome and permit further development and refinement of the biochemical specific locus test for in vivo mutagenesis studies in the mouse. A search for additional genetic polymorphisms in enzymes and other proteins is being conducted using live-trapped wild mice, interfertile subspecies of Mus musculus and a representative set of inbred strains. Protein preparations are analyzed by narrow range isoelectric focusing and other electrophoretic systems, coupled with various stains to visualize enzyme activities or protein. Initial efforts will concentrate on twenty enzymes which are polymorphic in humans but invariant among inbred strains of mice. As new variants are discovered, they will be placed on the C57BL/6J background by repeated back-crossing.